Re: alter user set local_preload_libraries.

On Thu, Jul 3, 2014 at 3:53 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Fujii Masao <masao(dot)fujii(at)gmail(dot)com> writes:
>> On Wed, Jul 2, 2014 at 11:15 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp> writes:
>>>> postgres=# alter user horiguti2 set local_preload_libraries='libname';
>>>> ERROR: parameter "local_preload_libraries" cannot be set after connection start
>
>>> Hm ... it's kind of annoying that that doesn't work; it's certainly not
>>> hard to imagine use-cases for per-user or per-database settings of
>>> local_preload_libraries. However, I'm not sure if we apply per-user or
>>> per-database settings early enough in backend startup that they could
>>> affect library loading. If we do, then the ALTER code needs to be
>>> taught to allow this.
>
>> ISTM that's what session_preload_libraries does.
>
> No, the reason for the distinction is that session_preload_libraries is
> superuser-only, and can load anything, while local_preload_libraries is
> (supposed to be) settable by ordinary users, and therefore is restricted
> to load only a subset of available libraries. But if you can't apply it
> via ALTER USER that seems like it takes away a lot of the value of having
> a non-SUSET GUC in this area.

Agreed. I was also thinking we can set it per role, but got surprised
when I found that's impossible. Is this a problem of only
local_preload_libraries? I'm afraid that all PGC_BACKEND parameters
have the same problem.

Regards,

--
Fujii Masao